Generally in the efforts hitherto made to provide an artificial heart or a pump capable of displacing blood and adapted to be implanted in the patient, a pneumatic or hydraulic drive for the displacement membrane was provided. Such devices require a massive support structure located outside the body and delivering energy to the membrane via the pneumatic or hydraulic fluid.
Consequently, efforts have been expanded in developing rotary pumps which can serve this purpose. In the discussion below, I will touch on some of the earlier pumps of this type provided for the displacement of blood or as artificial hearts or as circulation-assisting implanted pumps. I will also touch other rotary means, not specifically developed for use with blood which have structural similarity to the heart pump of this invention.
For example, the basic structure of the invention includes a pump chamber having a wall which is formed as a single lobe or two-lobe trochoid, respectively, in a 2:3 or 1:2 ratio with a rotor which has three corners or edges or two corners or edges, respectively, running along the trochoidal wall of the chamber and driven by an eccentric. These means are known for vastly different purposes, including so-called Wankel machines and are not suitable for use as heart pumps. The ratio referred to is the ratio between full revolutions of the motor to full revolutions of the driving eccentric.
For example, as described in the aforementioned copending application, when a single lobe chamber and the two-corner rotor device is used in a 1:2 ratio pump, the contact between the corners and the trochoidal wall can cause serious damage to the red blood corpuscles which are sheared between the wall and the rotor, thereby releasing hemoglobin and inducing premature heraolysis, which can be detrimental to a patient.
Trochoidal means with rotary pistons are described, for example in U.S. Pat. No. 3,221,664, in French patent No. 2,250,892, in French patent No. 2,260,008, in British patent No. 1,350,728, in German patent document DE-OS No. 2,021,513 and in Austrian Pat. No. 355,704, No. 355,177 and No. 351,137.
Not one of these references describes or suggests an effective electrically powered pump which can be utilized as an artificial heart or heart pump.
It is, therefore, interesting to note that most of the art dealing with artificial hearts or heart pumps has concentrate on membrane pumps whereby the force transmission between the pressure plate and the membrane is effected by a pneumatic or hydraulic fluid even if a pressure plate is electromechanically displaced.
However, in German patent document DE-OS No. 28 19 851, which is equivalent to French Pat. No. 2,389,382 and U.S. Pat. No. 4,296,500, a rotary pump using a trochoid rotary piston principle is described. This pump is generally similar in structure to the pump described in the publication "Einteilung der Rotations-kolbenmaschinen" by F. Wankel. To the extent that this pump can be utilized as an artificial heart it is driven by an electric motor outside the pump housing and many of the disadvantages of the other trochoidal rotary piston means described above are present here as well.
Mention may also be made of the publication "Pulsatile Flow Blow Pump based on the Principle of the Wankel Engine" by N. Verbiski et al. in the Journal of Thoracic and Cardiovascular Surgery, volume 57, No. 5, May 1969, pages 753-756, describing a 2:3 Wankel machine.
It is known to operate a membrane pump for the displacement of blood with an electromagnetic solenoid as well. The disadvantage of this arrangement, however, is that its size does not generally permit convenient implantation if it is to have sufficient blood displacement capacity. If the pump has a sufficiently small size to permit implantation, its capacity is insufficient.